<!DOCTYPE html>
<html lang="en" class="svg no-js">
<head>
    <meta charset="utf-8" />
    <!--[if IE ]>
    <meta http-equiv="X-UA-Compatible" content="IE=Edge,chrome=1" />
    <![endif]-->
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
        <meta name="Language" content="en">

    <title>MySQL :: MySQL 8.0 Reference Manual :: 29.4.2 Adding a New User-Defined Function</title>
    <link rel="stylesheet" media="all" href="css/main-20190125.min.css" />
            <link rel="stylesheet" media="all" href="css/docs-20190125.min.css" />
    
    
    <link rel="stylesheet" media="print" href="css/print-20190125.min.css" />

    
    
    
    
            <link rel="contents" href="index.html" title="MySQL 8.0 Reference Manual" />
<link rel="start" href="index.html" title="MySQL 8.0 Reference Manual" />
<link rel="prev" href="udf-features.html" title="29.4.1 Features of the User-Defined Function Interface" />
<link rel="next" href="udf-calling.html?ff=nopfpls" title="29.4.2.1 UDF Calling Sequences for Simple Functions" />
<link rel="up" href="adding-functions.html" title="29.4 Adding New Functions to MySQL" />

    
    <link rel="shortcut icon" href="favicon.ico" />
    <script>(function(H){ H.className=H.className.replace(/\bno-js\b/,'js') })(document.documentElement)</script>
    <script src="js/site-20181120.min.js"></script>

    
    
    
    <!--[if lt IE 9]>
        <script src="https://labs.mysql.com/common/js/polyfills/html5shiv-printshiv-3.7.2.min.js"></script>
        <script src="https://labs.mysql.com/common/js/polyfills/respond-1.4.2.min.js"></script>
    <![endif]-->
        <!--[if IE 9]>
        <style>#docs-sidebar-toc { box-sizing: content-box; }</style>
    <![endif]-->
    </head>

<body class="no-sidebar full-page dev">
<div class="page-wrapper">
    <header>

                        <a href="https://dev.mysql.com/" aria-label="Home" title="MySQL" id="l1-home-link"></a>
        
        <div id="l1-nav-container">
            <div id="l1-line1">
                <div id="l1-auth-links">
                    <a href="https://www.mysql.com/about/contact/"><b>Contact MySQL</b></a>
                    <span id="l1-contact-separator">&nbsp;|&nbsp;</span>
                    <span id="l1-contact-separator-br"><br /></span>
                                             <a href="https://dev.mysql.com/auth/login/?dest=https%3A%2F%2Fdev.mysql.com%2Fdoc%2Frefman%2F8.0%2Fen%2Fadding-udf.html">Login</a> &nbsp;|&nbsp;
                         <a href="https://dev.mysql.com/auth/register/">Register</a>
                                    </div>
                <div id="l1-lhs">
                    <div id="l1-slogan">
                        The world's most popular open source database
                    </div>
                    <div id="l1-search-box">
                        <form id="l1-search-form" method="get" action="https://www.oracle.com/search/results">
                        <input type="hidden" name="cat" value="mysql" />
                        <input type="hidden" name="Ntk" value="SI-ALL5" />
                        <input id="l1-search-input" type="search" class="icon-search" placeholder="Search" aria-label="Search" name="Ntt" />
                        </form>
                    </div>
                </div>
            </div>
            <div id="l1-line2">
                <div class="social-icons">
                    <a aria-label="Join us on Facebook" title="Join us on Facebook" href="http://www.facebook.com/mysql"><span class="icon-facebook"></span></a>
                    <a aria-label="Follow us on Twitter" title="Follow us on Twitter" href="https://twitter.com/mysql"><span class="icon-twitter"></span></a>
                    <a aria-label="Follow us on LinkedIn" title="Follow us on LinkedIn" href="https://www.linkedin.com/company/mysql"><span class="icon-linkedin"></span></a>
                    <a aria-label="Visit our YouTube channel" title="Visit our YouTube channel" href="http://www.youtube.com/mysqlchannel"><span class="icon-youtube"></span></a>
                </div>
                <ul id="l1-nav">
                    <li>
                        <a href="https://www.mysql.com/"><!-- <span class="icon-sakila"></span>  -->MySQL.com</a>
                    </li><li>
                        <a href="https://www.mysql.com/downloads/"><!-- <span class="icon-download-thin"></span>  -->Downloads</a>
                    </li><li class="active">
                        <a href="/doc/"><!-- <span class="icon-books"></span>  -->Documentation</a>
                    </li><li>
                        <a href="/"><!-- <span class="icon-code"></span>  -->Developer Zone</a>
                    </li>                </ul>
            </div>
        </div>
        <div id="sub-header">
            <div id="l2-nav-container">
                <div id="l2-nav-toggle">
                    <span class="icon-three-bars"></span>
                </div>
                                                                                        <a class="button nav-button-3" href="/"><span class="icon-code"></span> Developer Zone</a>
                                                                                                                                    <a class="button nav-button-2" href="https://www.mysql.com/downloads/"><span class="icon-download-thin"></span> Downloads</a>
                                                                                                <a class="button nav-button-1" href="https://www.mysql.com/"><span class="icon-sakila"></span> MySQL.com</a>
                                                                        <div id="l2-search-toggle">
                    <span class="icon-search"></span>
                </div>
                <div id="l2-site-icon">
                                                                                                                                                                                                    <span class="icon-books"></span>
                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                        </div>
                <div id="l1-section-title">
                    <span id="l1-section-label">
                        <a href="/doc/">Documentation</a>
                    </span>
                </div>
                <nav>
                    

<ul id="l2-nav">
            	<li class="active"><a class="active " href="/doc/refman/en/">MySQL Server</a>
    			</li>
	        	<li class=""><a  href="/doc/index-enterprise.html">MySQL Enterprise</a>
    			</li>
	        	<li class=""><a  href="/doc/workbench/en/">Workbench</a>
    			</li>
	        	<li class=""><a  href="/doc/en/mysql-innodb-cluster-userguide.html">InnoDB Cluster</a>
    			</li>
	        	<li class=""><a  href="/doc/index-cluster.html">MySQL NDB Cluster</a>
    			</li>
	        	<li class=""><a  href="/doc/index-connectors.html">Connectors</a>
    			</li>
	        	<li class=" last"><a  href="/doc/index-other.html">More</a>
    			</li>
	                        <li class="other-section"><a href="https://www.mysql.com/">MySQL.com</a></li>
                            <li class="other-section"><a href="https://www.mysql.com/downloads/">Downloads</a></li>
                                        <li class="other-section"><a href="/">Developer Zone</a></li>
            </ul>
                </nav>
            </div>
            <div id="l3-search-container"></div>
            <div id="top-orange"><span id="section-nav">Section Menu: &nbsp; </span></div>
        </div>
    </header>
        <div id="page">
                        <div role="main" id="main">

            
                
            
<div>
    <div id="docs-sidebar-toc" class="">
    <div id="docs-toc-inner">
        <div class="docs-sidebar-header" id="docs-nav-header">
            <a class="docs-show-hide-nav" id="docs-hide-nav" href="" title="Hide Sidebar" aria-label="Hide Sidebar"><span class="icon-arrow-small-left"></span></a>
            <div class="docs-nav-links">
                                    
    <a href="udf-features.html"
        aria-label="Previous" title="Previous: Features of the User-Defined Function Interface"><span
        class="icon-chevron-left"></span></a>
<a href="index.html" aria-label="Start" title="Start"><span class="icon-book-open"></span></a>
        <a aria-label="Up" href="adding-functions.html" title="Up: Adding New Functions to MySQL"><span class="icon-chevron-up"></span></a>
    <a href="udf-calling.html" aria-label="Next"
        title="Next: UDF Calling Sequences for Simple Functions"><span
        class="icon-chevron-right"></span></a>
                            </div>
        </div>
                    
<div id="docs-sidebar-search-container">
    <div id="docs-sidebar-search-box">
        <form method="get" action="/mysql-manual/search-page">
            <input type="hidden" name="d" id="d" value="201" />
            <input type="hidden" name="p" id="p" value="1" />
            <input type="text" name="keyword" id="q" title="Search this Manual"
                value=""
                style="color: #bbb;"
                onfocus=""
                onblur="" />

            <button class="docs-sidebar-search-btn" aria-label="Search" title="Search" type="submit">
                <span class="icon-search"></span>
            </button>
        </form>
    </div>
</div>
                <div class="docs-sidebar-nav">
            <a class="docs-icon-home" href="/doc/"><span class="icon-home"></span>Documentation Home</a><hr />
            <div class="docs-sidebar-mtitle">MySQL 8.0 Reference Manual</div>
            <nav class="doctoc" id="doc-201">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="preface.html">Preface and Legal Notices</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="introduction.html">General Information</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="installing.html">Installing and Upgrading MySQL</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="tutorial.html">Tutorial</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="programs.html">MySQL Programs</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="server-administration.html">MySQL Server Administration</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="security.html">Security</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="backup-and-recovery.html">Backup and Recovery</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="optimization.html">Optimization</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="language-structure.html">Language Structure</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="charset.html">Character Sets, Collations, Unicode</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="data-types.html">Data Types</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="functions.html">Functions and Operators</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="sql-syntax.html">SQL Statement Syntax</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="data-dictionary.html">MySQL Data Dictionary</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="innodb-storage-engine.html">The InnoDB Storage Engine</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="storage-engines.html">Alternative Storage Engines</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="replication.html">Replication</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="group-replication.html">Group Replication</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="mysql-shell-userguide.html">MySQL Shell</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="document-store.html">Using MySQL as a Document Store</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="mysql-innodb-cluster-userguide.html">InnoDB Cluster</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="mysql-cluster.html">MySQL NDB Cluster 8.0</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="partitioning.html">Partitioning</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="stored-objects.html">Stored Objects</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="information-schema.html">INFORMATION_SCHEMA Tables</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="performance-schema.html">MySQL Performance Schema</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="sys-schema.html">MySQL sys Schema</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="connectors-apis.html">Connectors and APIs</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-down"></span></a></div><div class="docs-sidebar-nav-link"><a href="extending-mysql.html">Extending MySQL</a></div></div>                        <div class="docs-submenu">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="mysql-internals.html">MySQL Internals</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="mysql-threads.html">MySQL Threads</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="mysql-test-suite.html">The MySQL Test Suite</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="plugin-api.html">The MySQL Plugin API</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="plugin-types.html">Types of Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="plugin-api-characteristics.html">Plugin API Characteristics</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="plugin-api-components.html">Plugin API Components</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="writing-plugins.html">Writing Plugins</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-plugins-overview.html">Overview of Plugin Writing</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="plugin-data-structures.html">Plugin Data Structures</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="compiling-plugin-libraries.html">Compiling and Installing Plugin Libraries</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-full-text-plugins.html">Writing Full-Text Parser Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-daemon-plugins.html">Writing Daemon Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-information-schema-plugins.html">Writing INFORMATION_SCHEMA Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-semisynchronous-replication-plugins.html">Writing Semisynchronous Replication Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-audit-plugins.html">Writing Audit Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-authentication-plugins.html">Writing Authentication Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-password-validation-plugins.html">Writing Password-Validation Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-protocol-trace-plugins.html">Writing Protocol Trace Plugins</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="writing-keyring-plugins.html">Writing Keyring Plugins</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="plugin-services.html">MySQL Services for Plugins</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="locking-service.html">The Locking Service</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="locking-service-c-interface.html">The Locking Service C Interface</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="locking-service-udf-interface.html">The Locking Service UDF Interface</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="keyring-service.html">The Keyring Service</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-down"></span></a></div><div class="docs-sidebar-nav-link"><a href="adding-functions.html">Adding New Functions to MySQL</a></div></div>                        <div class="docs-submenu">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-features.html">Features of the User-Defined Function Interface</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-down"></span></a></div><div class="docs-sidebar-nav-link current"><a href="adding-udf.html">Adding a New User-Defined Function</a></div></div>                        <div class="docs-submenu">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-calling.html">UDF Calling Sequences for Simple Functions</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-aggr-calling.html">UDF Calling Sequences for Aggregate Functions</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-arguments.html">UDF Argument Processing</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-return-values.html">UDF Return Values and Error Handling</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-compiling.html">UDF Compiling and Installing</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="udf-security.html">UDF Security Precautions</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="adding-native-function.html">Adding a New Native Function</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="porting.html">Debugging and Porting MySQL</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable  loaded" aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="debugging-server.html">Debugging a MySQL Server</a></div></div>                        <div class="docs-submenu hidden">
                                    
    <ul>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="compiling-for-debugging.html">Compiling MySQL for Debugging</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="making-trace-files.html">Creating Trace Files</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="making-windows-dumps.html">Using WER with PDB to create a Windows crashdump</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="using-gdb-on-mysqld.html">Debugging mysqld under gdb</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="using-stack-trace.html">Using a Stack Trace</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="using-log-files.html">Using Server Logs to Find Causes of Errors in mysqld</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="reproducible-test-case.html">Making a Test Case If You Experience Table Corruption</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="debugging-client.html">Debugging a MySQL Client</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="lock-order-tool.html">The LOCK_ORDER Tool</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="dbug-package.html">The DBUG Package</a></div></div>                    </li>
        </ul>
                            </div>
                    </li>
        </ul>
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="mysql-enterprise.html">MySQL Enterprise Edition</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="workbench.html">MySQL Workbench</a></div></div>                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="faqs.html">MySQL 8.0 Frequently Asked Questions</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="error-handling.html">Errors, Error Codes, and Common Problems</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="restrictions.html">Restrictions and Limits</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><a class="expandable " aria-label="Subnav" href=""><span class="icon-chevron-right"></span></a></div><div class="docs-sidebar-nav-link"><a href="indexes.html">Indexes</a></div></div>                        <div class="docs-submenu hidden">
                            </div>
                    </li>
            <li>
            <div><div class="docs-sidebar-nav-icon"><span class="icon-dot"></span></div><div class="docs-sidebar-nav-link"><a href="glossary.html">MySQL Glossary</a></div></div>                    </li>
        </ul>
                            </nav>
        </div>

        
<a class="docs-sidebar-section" href=""><span class="icon-related"></span>
    <span class="text">Related Documentation</span></a>
<div class="docs-sidebar-accordian open">
    <div class="text">
        <a href="/doc/relnotes/mysql/8.0/en/">MySQL 8.0 Release Notes</a><br />
        <a href="/doc/dev/mysql-server/latest/">MySQL 8.0 Source Code Documentation</a><br />
        </div>
</div>

    <a class="docs-sidebar-section" href=""><span class="icon-download-thin"></span>
        <span class="text">
            Download
                            this Manual
                    </span>
    </a>
    <div class="docs-sidebar-accordian open">
        <div class="text">
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.pdf">PDF (US Ltr)</a>
            - 46.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.a4.pdf">PDF (A4)</a>
            - 46.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-ref-manual-8.0-en-pdf-1-20190611.noarch.rpm">PDF (RPM)</a>
            - 41.5Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.html-chapter.tar.gz">HTML Download (TGZ)</a>
            - 10.6Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.html-chapter.zip">HTML Download (Zip)</a>
            - 10.6Mb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-ref-manual-8.0-en-html-chapter-1-20190611.noarch.rpm">HTML Download (RPM)</a>
            - 9.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.man-gpl.tar.gz">Man Pages (TGZ)</a>
            - 220.4Kb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.man-gpl.zip">Man Pages (Zip)</a>
            - 325.8Kb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-8.0.info.gz">Info (Gzip)</a>
            - 4.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-8.0.info.zip">Info (Zip)</a>
            - 4.1Mb<br />
                    </div>
    </div>

<a class="docs-sidebar-section" href=""><span class="icon-book"></span>
    <span class="text">Excerpts from this Manual</span></a>
<div class="docs-sidebar-accordian">
    <div class="text">
                <a href="/doc/mysql-backup-excerpt/8.0/en/">MySQL Backup and Recovery</a><br />
                <a href="/doc/mysql-g11n-excerpt/8.0/en/">MySQL Globalization</a><br />
                <a href="/doc/mysql-infoschema-excerpt/8.0/en/">MySQL Information Schema</a><br />
                <a href="/doc/mysql-installation-excerpt/8.0/en/">MySQL Installation Guide</a><br />
                <a href="/doc/mysql-security-excerpt/8.0/en/">Security in MySQL</a><br />
                <a href="/doc/mysql-startstop-excerpt/8.0/en/">Starting and Stopping MySQL</a><br />
                <a href="/doc/mysql-linuxunix-excerpt/8.0/en/">MySQL and Linux/Unix</a><br />
                <a href="/doc/mysql-windows-excerpt/8.0/en/">MySQL and Windows</a><br />
                <a href="/doc/mysql-osx-excerpt/8.0/en/">MySQL and OS X</a><br />
                <a href="/doc/mysql-solaris-excerpt/8.0/en/">MySQL and Solaris</a><br />
                <a href="/doc/mysql-sourcebuild-excerpt/8.0/en/">Building MySQL from Source</a><br />
                <a href="/doc/mysql-reslimits-excerpt/8.0/en/">MySQL Restrictions and Limitations</a><br />
                <a href="/doc/mysql-partitioning-excerpt/8.0/en/">MySQL Partitioning</a><br />
                <a href="/doc/mysql-secure-deployment-guide/8.0/en/">MySQL Secure Deployment Guide</a><br />
                <a href="/doc/mysql-tutorial-excerpt/8.0/en/">MySQL Tutorial</a><br />
                <a href="/doc/mysql-perfschema-excerpt/8.0/en/">MySQL Performance Schema</a><br />
                <a href="/doc/mysql-replication-excerpt/8.0/en/">MySQL Replication</a><br />
                <a href="/doc/mysql-repo-excerpt/8.0/en/">Using the MySQL Yum Repository</a><br />
            </div>
</div>

        <br /><span id="wkr"><br /></span>
    </div>
    </div>

    <div id="docs-main" class="has-toc">
    <div id="docs-main-inner">

                <div class="right" id="docs-version-nav">
            <a href="" id="docs-version-nav-toggle">version 8.0
            <span class="icon-chevron-down"></span></a>
            <div id="docs-version-list">
                                                                                            <a                         href="/doc/refman/5.7/en/adding-udf.html">
                        5.7
                                            </a><br />
                                                                            <a                         href="/doc/refman/5.6/en/adding-udf.html">
                        5.6
                                            </a><br />
                                                                            <a                         href="/doc/refman/5.5/en/adding-udf.html">
                        5.5
                                            </a><br />
                                                                        <div id="docs-version-nav-lang">
                                                                                                                                                    <a                                     href="/doc/refman/5.6/ja/adding-udf.html">
                                    5.6&nbsp;
                                                                            Japanese
                                                                    </a><br />
                                                                                            </div>
                            </div>
        </div>
        
        <div id="docs-show-nav" class="left hidden" style="margin-right: 15px;">
            <a class="docs-show-hide-nav" href="" aria-label="Show Sidebar"
                title="Show Sidebar"><span class="icon-arrow-small-right"></span></a>
        </div>

                        <div id="docs-breadcrumbs">
            <a href="/doc/refman/8.0/en/">MySQL 8.0 Reference Manual</a> &nbsp;/&nbsp;
                            <span id="breadcrumbs-link"><a href="" id="show-breadcrumbs">...</a> &nbsp;/&nbsp;</span>
                <span class="hidden" id="hidden-breadcrumbs">
                                                        <a href="extending-mysql.html">Extending MySQL</a> &nbsp;/&nbsp;
                                                            <a href="adding-functions.html">Adding New Functions to MySQL</a> &nbsp;/&nbsp;
                                                                                        </span>
                                        Adding a New User-Defined Function
                                    </div>
        
        <div id="docs-body">
        
<div class="section">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a name="adding-udf"></a>29.4.2 Adding a New User-Defined Function</h3>

</div>

</div>

</div>
<div class="toc">
<p><small>[<a href="#" class="tocdetail" onclick="toggle('tocdetail-0'); return false;" onkeypress="if (event.keyCode == 13) { toggle('tocdetail-0'); return false;}">+/-</a>]</small></p>
<dl id="tocdetail-0"><dt><span class="section"><a href="udf-calling.html">29.4.2.1 UDF Calling Sequences for Simple Functions</a></span></dt><dt><span class="section"><a href="udf-aggr-calling.html">29.4.2.2 UDF Calling Sequences for Aggregate Functions</a></span></dt><dt><span class="section"><a href="udf-arguments.html">29.4.2.3 UDF Argument Processing</a></span></dt><dt><span class="section"><a href="udf-return-values.html">29.4.2.4 UDF Return Values and Error Handling</a></span></dt><dt><span class="section"><a href="udf-compiling.html">29.4.2.5 UDF Compiling and Installing</a></span></dt><dt><span class="section"><a href="udf-security.html">29.4.2.6 UDF Security Precautions</a></span></dt></dl>
</div>
<a class="indexterm" name="idm139663050135296"></a><a class="indexterm" name="idm139663050133840"></a><a class="indexterm" name="idm139663050132352"></a><p>
        For the UDF mechanism to work, functions must be written in C or
        C++ and your operating system must support dynamic loading.
        MySQL source distributions include a file
        <code class="filename">sql/udf_example.cc</code> that defines five UDF
        functions. Consult this file to see how UDF calling conventions
        work. The <code class="filename">include/mysql_com.h</code> header file
        defines UDF-related symbols and data structures, although you
        need not include this header file directly; it is included by
        <code class="filename">mysql.h</code>.
      </p><p>
        A UDF contains code that becomes part of the running server, so
        when you write a UDF, you are bound by any and all constraints
        that apply to writing server code. For example, you may have
        problems if you attempt to use functions from the
        <code class="literal">libstdc++</code> library. These constraints may
        change in future versions of the server, so it is possible that
        server upgrades will require revisions to UDFs that were
        originally written for older servers. For information about
        these constraints, see
        <a class="xref" href="source-configuration-options.html" title="2.9.4 MySQL Source-Configuration Options">Section 2.9.4, “MySQL Source-Configuration Options”</a>, and
        <a class="xref" href="compilation-problems.html" title="2.9.5 Dealing with Problems Compiling MySQL">Section 2.9.5, “Dealing with Problems Compiling MySQL”</a>.
      </p><p>
        To be able to use UDFs, you must link <a class="link" href="mysqld.html" title="4.3.1 mysqld — The MySQL Server"><span class="command"><strong>mysqld</strong></span></a>
        dynamically. If you want to use a UDF that needs to access
        symbols from <a class="link" href="mysqld.html" title="4.3.1 mysqld — The MySQL Server"><span class="command"><strong>mysqld</strong></span></a> (for example, the
        <code class="literal">metaphone</code> function in
        <code class="filename">sql/udf_example.cc</code> uses
        <code class="literal">default_charset_info</code>), you must link the
        program with <code class="option">-rdynamic</code> (see <code class="literal">man
        dlopen</code>).
      </p><p>
        For each function that you want to use in SQL statements, you
        should define corresponding C (or C++) functions. In the
        following discussion, the name <span class="quote">“<span class="quote">xxx</span>”</span> is used for an
        example function name. To distinguish between SQL and C/C++
        usage, <code class="literal">XXX()</code> (uppercase) indicates an SQL
        function call, and <code class="literal">xxx()</code> (lowercase)
        indicates a C/C++ function call.
</p>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">

<div class="admon-title">
Note
</div>
<p>
          When using C++ you can encapsulate your C functions within:
        </p><pre class="programlisting copytoclipboard line-numbers language-c one-line"><code class="language-c">extern "C" { ... }</code></pre><p>
          This ensures that your C++ function names remain readable in
          the completed UDF.
</p>
</div>
<p>
        The following list describes the C/C++ functions that you write
        to implement the interface for a function named
        <code class="literal">XXX()</code>. The main function,
        <code class="literal">xxx()</code>, is required. In addition, a UDF
        requires at least one of the other functions described here, for
        reasons discussed in <a class="xref" href="udf-security.html" title="29.4.2.6 UDF Security Precautions">Section 29.4.2.6, “UDF Security Precautions”</a>.
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
            <code class="literal">xxx()</code>
          </p><p>
            The main function. This is where the function result is
            computed. The correspondence between the SQL function data
            type and the return type of your C/C++ function is shown
            here.
</p>
<div class="informaltable">
<a name="adding-udf-sql-c-cpp-data-types"></a><table summary="SQL function data types and corresponding C/C++ data types."><col width="25%"><col width="25%"><thead><tr>
                <th scope="col">SQL Type</th>
                <th scope="col">C/C++ Type</th>
              </tr></thead><tbody><tr>
                <td scope="row"><code class="literal">STRING</code></td>
                <td><code class="literal">char *</code></td>
              </tr><tr>
                <td scope="row"><a class="link" href="integer-types.html" title="11.2.1 Integer Types (Exact Value) - INTEGER, INT, SMALLINT, TINYINT, MEDIUMINT, BIGINT"><code class="literal">INTEGER</code></a></td>
                <td><code class="literal">long long</code></td>
              </tr><tr>
                <td scope="row"><a class="link" href="floating-point-types.html" title="11.2.3 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE"><code class="literal">REAL</code></a></td>
                <td><code class="literal">double</code></td>
</tr></tbody></table>
</div>
<p>
            It is also possible to declare a
            <a class="link" href="fixed-point-types.html" title="11.2.2 Fixed-Point Types (Exact Value) - DECIMAL, NUMERIC"><code class="literal">DECIMAL</code></a> function, but
            currently the value is returned as a string, so you should
            write the UDF as though it were a <code class="literal">STRING</code>
            function. <code class="literal">ROW</code> functions are not
            implemented.
          </p></li><li class="listitem"><p>
            <code class="literal">xxx_init()</code>
          </p><p>
            The initialization function for <code class="literal">xxx()</code>. If
            present, it can be used for the following purposes:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: circle; "><li class="listitem"><p>
                To check the number of arguments to
                <code class="literal">XXX()</code>.
              </p></li><li class="listitem"><p>
                To verify that the arguments are of a required type or,
                alternatively, to tell MySQL to coerce arguments to the
                required types when the main function is called.
              </p></li><li class="listitem"><p>
                To allocate any memory required by the main function.
              </p></li><li class="listitem"><p>
                To specify the maximum length of the result.
              </p></li><li class="listitem"><p>
                To specify (for <a class="link" href="floating-point-types.html" title="11.2.3 Floating-Point Types (Approximate Value) - FLOAT, DOUBLE"><code class="literal">REAL</code></a>
                functions) the maximum number of decimal places in the
                result.
              </p></li><li class="listitem"><p>
                To specify whether the result can be
                <code class="literal">NULL</code>.
</p></li></ul>
</div>
</li><li class="listitem"><p>
            <code class="literal">xxx_deinit()</code>
          </p><p>
            The deinitialization function for <code class="literal">xxx()</code>.
            If present, it should deallocate any memory allocated by the
            initialization function.
</p></li></ul>
</div>
<p>
        When an SQL statement invokes <code class="literal">XXX()</code>, MySQL
        calls the initialization function <code class="literal">xxx_init()</code>
        to let it perform any required setup, such as argument checking
        or memory allocation. If <code class="literal">xxx_init()</code> returns
        an error, MySQL aborts the SQL statement with an error message
        and does not call the main or deinitialization functions.
        Otherwise, MySQL calls the main function
        <code class="literal">xxx()</code> once for each row. After all rows have
        been processed, MySQL calls the deinitialization function
        <code class="literal">xxx_deinit()</code> so that it can perform any
        required cleanup.
      </p><p>
        For aggregate functions that work like
        <a class="link" href="group-by-functions.html#function_sum"><code class="literal">SUM()</code></a>, you must also provide the
        following functions:
</p>
<div class="itemizedlist">
<ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
            <code class="literal">xxx_clear()</code>
          </p><p>
            Reset the current aggregate value but do not insert the
            argument as the initial aggregate value for a new group.
          </p></li><li class="listitem"><p>
            <code class="literal">xxx_add()</code>
          </p><p>
            Add the argument to the current aggregate value.
</p></li></ul>
</div>
<p>
        MySQL handles aggregate UDFs as follows:
</p>
<div class="orderedlist">
<ol class="orderedlist" type="1"><li class="listitem"><p>
            Call <code class="literal">xxx_init()</code> to let the aggregate
            function allocate any memory it needs for storing results.
          </p></li><li class="listitem"><p>
            Sort the table according to the <code class="literal">GROUP BY</code>
            expression.
          </p></li><li class="listitem"><p>
            Call <code class="literal">xxx_clear()</code> for the first row in
            each new group.
          </p></li><li class="listitem"><p>
            Call <code class="literal">xxx_add()</code> for each row that belongs
            in the same group.
          </p></li><li class="listitem"><p>
            Call <code class="literal">xxx()</code> to get the result for the
            aggregate when the group changes or after the last row has
            been processed.
          </p></li><li class="listitem"><p>
            Repeat steps 3 to 5 until all rows has been processed
          </p></li><li class="listitem"><p>
            Call <code class="literal">xxx_deinit()</code> to let the UDF free any
            memory it has allocated.
</p></li></ol>
</div>
<p>
        All functions must be thread-safe. This includes not just the
        main function, but the initialization and deinitialization
        functions as well, and also the additional functions required by
        aggregate functions. A consequence of this requirement is that
        you are not permitted to allocate any global or static variables
        that change! If you need memory, you should allocate it in
        <code class="literal">xxx_init()</code> and free it in
        <code class="literal">xxx_deinit()</code>.
</p>
</div><br />
        </div>

                <div id="docs-in-page-nav-container">
            <div id="docs-in-page-nav">
                
    <a href="udf-features.html"
        aria-label="Previous" title="Previous: Features of the User-Defined Function Interface"><span
        class="icon-chevron-left"></span> PREV</a> &nbsp;
<a href="index.html" aria-label="Start" title="Start"> HOME</a> &nbsp;
        <a aria-label="Up" href="adding-functions.html" title="Up: Adding New Functions to MySQL"> UP</a> &nbsp;
    <a href="udf-calling.html" aria-label="Next"
        title="Next: UDF Calling Sequences for Simple Functions">NEXT <span
        class="icon-chevron-right"></span></a>
            </div>
        </div>
        
         <div id="docs-body-extra">
             
<a class="docs-sidebar-section" href=""><span class="icon-related"></span>
    <span class="text">Related Documentation</span></a>
<div class="docs-sidebar-accordian">
    <div class="text">
        <a href="/doc/relnotes/mysql/8.0/en/">MySQL 8.0 Release Notes</a><br />
        <a href="/doc/dev/mysql-server/latest/">MySQL 8.0 Source Code Documentation</a><br />
        </div>
</div>

    <a class="docs-sidebar-section" href=""><span class="icon-download-thin"></span>
        <span class="text">
            Download
                            this Manual
                    </span>
    </a>
    <div class="docs-sidebar-accordian">
        <div class="text">
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.pdf">PDF (US Ltr)</a>
            - 46.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.a4.pdf">PDF (A4)</a>
            - 46.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-ref-manual-8.0-en-pdf-1-20190611.noarch.rpm">PDF (RPM)</a>
            - 41.5Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.html-chapter.tar.gz">HTML Download (TGZ)</a>
            - 10.6Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.html-chapter.zip">HTML Download (Zip)</a>
            - 10.6Mb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-ref-manual-8.0-en-html-chapter-1-20190611.noarch.rpm">HTML Download (RPM)</a>
            - 9.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.man-gpl.tar.gz">Man Pages (TGZ)</a>
            - 220.4Kb<br />
                        <a href="https://downloads.mysql.com/docs/refman-8.0-en.man-gpl.zip">Man Pages (Zip)</a>
            - 325.8Kb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-8.0.info.gz">Info (Gzip)</a>
            - 4.1Mb<br />
                        <a href="https://downloads.mysql.com/docs/mysql-8.0.info.zip">Info (Zip)</a>
            - 4.1Mb<br />
                    </div>
    </div>

<a class="docs-sidebar-section" href=""><span class="icon-book"></span>
    <span class="text">Excerpts from this Manual</span></a>
<div class="docs-sidebar-accordian">
    <div class="text">
                <a href="/doc/mysql-backup-excerpt/8.0/en/">MySQL Backup and Recovery</a><br />
                <a href="/doc/mysql-g11n-excerpt/8.0/en/">MySQL Globalization</a><br />
                <a href="/doc/mysql-infoschema-excerpt/8.0/en/">MySQL Information Schema</a><br />
                <a href="/doc/mysql-installation-excerpt/8.0/en/">MySQL Installation Guide</a><br />
                <a href="/doc/mysql-security-excerpt/8.0/en/">Security in MySQL</a><br />
                <a href="/doc/mysql-startstop-excerpt/8.0/en/">Starting and Stopping MySQL</a><br />
                <a href="/doc/mysql-linuxunix-excerpt/8.0/en/">MySQL and Linux/Unix</a><br />
                <a href="/doc/mysql-windows-excerpt/8.0/en/">MySQL and Windows</a><br />
                <a href="/doc/mysql-osx-excerpt/8.0/en/">MySQL and OS X</a><br />
                <a href="/doc/mysql-solaris-excerpt/8.0/en/">MySQL and Solaris</a><br />
                <a href="/doc/mysql-sourcebuild-excerpt/8.0/en/">Building MySQL from Source</a><br />
                <a href="/doc/mysql-reslimits-excerpt/8.0/en/">MySQL Restrictions and Limitations</a><br />
                <a href="/doc/mysql-partitioning-excerpt/8.0/en/">MySQL Partitioning</a><br />
                <a href="/doc/mysql-secure-deployment-guide/8.0/en/">MySQL Secure Deployment Guide</a><br />
                <a href="/doc/mysql-tutorial-excerpt/8.0/en/">MySQL Tutorial</a><br />
                <a href="/doc/mysql-perfschema-excerpt/8.0/en/">MySQL Performance Schema</a><br />
                <a href="/doc/mysql-replication-excerpt/8.0/en/">MySQL Replication</a><br />
                <a href="/doc/mysql-repo-excerpt/8.0/en/">Using the MySQL Yum Repository</a><br />
            </div>
</div>
         </div>

              </div>
     </div>

</div>

<script>
$(function() {
    var doc = new $.doc({ 'mobile': $.browser.mobile, 'docId': 1, 'highlight': true });
});
</script>
    

            
        </div>
    </div>

    <footer class="collapsed">
        <div id="footer-bottom">
                                    <div id="footer-collapse">
                <a href="" id="expand-footer"
                    aria-label="Expand Footer"
                    title="Expand Footer"><span
                    class="icon-plus-square"></span></a>
            </div>
                        <div class="footer-contact">
                <div id="footer-contact-icon" style="display: none;">
                    <span class="icon-call-phone"></span>
                </div>
                <div id="footer-contact-numbers" style="display: none;">
                    <strong>Contact MySQL Sales</strong><br/>
                    USA/Canada: +1-866-221-0634 &nbsp;
                    (<a href="https://www.mysql.com/about/contact/phone/">More Countries &raquo;</a>)
                </div>
                <div id="footer-contact-copyright" style="display: inline-block;">
                    <a href="http://www.oracle.com/" aria-label="Oracle" title="Oracle"><span class="oracle-logo"></span></a>
                    &nbsp; &copy; 2019, Oracle Corporation and/or its affiliates
                </div>
            </div>
            <div class="social-icons">
                <a aria-label="Join us on Facebook" title="Join us on Facebook" href="http://www.facebook.com/mysql"><span class="icon-facebook-square"></span></a>
                <a aria-label="Follow us on Twitter" title="Follow us on Twitter" href="https://twitter.com/mysql"><span class="icon-twitter-square"></span></a>
                <a aria-label="Follow us on LinkedIn" title="Follow us on LinkedIn" href="https://www.linkedin.com/company/mysql"><span class="icon-linkedin-square"></span></a>
                <a aria-label="Visit our YouTube channel" title="Visit our YouTube channel" href="http://www.youtube.com/mysqlchannel"><span class="icon-youtube-square"></span></a>
            </div>
            <br class="clear" />
        </div>
        <div id="footer-links">

            <div id="footer-nav"></div>

            <div class="links">
                <ul>
                    <li class="top"><a href="https://www.mysql.com/products/">Products</a></li>
                    <li><a href="https://www.mysql.com/cloud/">Oracle MySQL Cloud Service</a></li>
                    <li><a href="https://www.mysql.com/products/enterprise/">MySQL Enterprise Edition</a></li>
                    <li><a href="https://www.mysql.com/products/standard/">MySQL Standard Edition</a></li>
                    <li><a href="https://www.mysql.com/products/classic/">MySQL Classic Edition</a></li>
                    <li><a href="https://www.mysql.com/products/cluster/">MySQL Cluster CGE</a></li>
                    <li><a href="https://www.mysql.com/oem/">MySQL Embedded (OEM/ISV)</a></li>
                </ul>
            </div>

            <div class="links">
                <ul>
                    <li class="top"><a href="https://www.mysql.com/services/">Services</a></li>
                    <li><a href="https://www.mysql.com/training/">Training</a></li>
                    <li><a href="https://www.mysql.com/certification/">Certification</a></li>
                    <li><a href="https://www.mysql.com/consulting/">Consulting</a></li>
                    <li><a href="https://www.mysql.com/support/">Support</a></li>
                </ul>
            </div>

            <div class="links">
                <ul>
                    <li class="top"><a href="https://dev.mysql.com/downloads/">Downloads</a></li>
                    <li><a href="https://dev.mysql.com/downloads/mysql/">MySQL Community Server</a></li>
                    <li><a href="https://dev.mysql.com/downloads/cluster/">MySQL NDB Cluster</a></li>
                    <li><a href="https://dev.mysql.com/downloads/shell/">MySQL Shell</a></li>
                    <li><a href="https://dev.mysql.com/downloads/router/">MySQL Router</a></li>
                    <li><a href="https://dev.mysql.com/downloads/workbench/">MySQL Workbench</a></li>
                </ul>
            </div>

            <div class="links">
                <ul>
                    <li class="top"><a href="https://dev.mysql.com/doc/">Documentation</a></li>
                    <li><a href="https://dev.mysql.com/doc/refman/en/">MySQL Reference Manual</a></li>
                    <li><a href="https://dev.mysql.com/doc/workbench/en/">MySQL Workbench</a></li>
                    <li><a href="https://dev.mysql.com/doc/index-cluster.html">MySQL NDB Cluster</a></li>
                    <li><a href="https://dev.mysql.com/doc/index-connectors.html">MySQL Connectors</a></li>
                    <li><a href="https://dev.mysql.com/doc/#topic">Topic Guides</a></li>
                </ul>
            </div>

            <div class="links">
                <ul>
                    <li class="top"><a href="https://www.mysql.com/about/">About MySQL</a></li>
                    <li><a href="https://www.mysql.com/about/contact/">Contact Us</a></li>
                                                            <li><a href="https://www.mysql.com/buy-mysql/">How to Buy</a></li>
                    <li><a href="https://www.mysql.com/partners/">Partners</a></li>
                    <li><a href="https://www.mysql.com/about/jobs/">Job Opportunities</a></li>
                    <li><a href="https://www.mysql.com/sitemap.html">Site Map</a></li>
                </ul>
            </div>

            
            <div id="footer-logo">
                <a href="http://www.oracle.com/" aria-label="Oracle" title="Oracle"><span class="oracle-logo"></span></a>
                &nbsp; &copy; 2019, Oracle Corporation and/or its affiliates
                <div class="footer-legal-links">
                    <a href="https://www.mysql.com/about/legal/">Legal Policies</a> |
                    <a href="http://www.oracle.com/us/legal/privacy/index.htm">Your Privacy Rights</a> |
                    <a href="http://www.oracle.com/us/legal/terms/index.html">Terms of Use</a> |
                    <a href="http://www.oracle.com/us/legal/third-party-trademarks/index.html">Trademark Policy</a> |
                    <a href="http://www.oracle.com/technetwork/community/oca-486395.html">Contributor Agreement</a> |
                    <div id="teconsent" style="display: inline-block"><script async="async" type="text/javascript" src="js/notice.js" crossorigin=""></script></div>
                </div>
            </div>

        </div>
    </footer>
</div>

        <script src="js/s_code_remote.js"></script>

        
    
</body>
</html>
